Distillation process for separating butyraldehyde from ethyl acetate



M y 2, 1953 T. Q. ELIOT 2,638,442

DISTILLATION PROCESS FOR SEPARATING BUTYRALDEHYDE FROM ETHYL ACETATE Filed Oct. 20, 1949 DRY BUTYRALDEHYDE To SEWER DRY BUTYRALDEHYDE To FURTHER pnocgssms INVENTOR.

, I T 9813/0 o BY Qj ATTORNEY WATER FEVED Patented May 12, 1953 DISTILLATION PROCESS FOR SEPARATING BUTYRALDEHYDE FROM ETHYL ACETATE Theodore Q. Eliot, Tulsa, Okla., assignor to Stanolind Oil and Gas Company, Tulsa, Okla., a corporation of Delaware Application October 20, 1949, Serial No. 122,524

6 Claims. (01. 202 395) separating butyraldehyde from ethyl acetate occurs in numerous purification processes, one of the principal instances where an efficient method for the separation of these two chemi cals is most urgently needed is in their recovery, along with other'chemicals, from the aqueous fraction produced by the reduction of carbon monoxide with hydrogen under known synthesis conditions. The magnitude of this problem may be more fully appreciated when it is realized that in hydrocarbon synthesis plants designed for commercial operation and having a capacity in the neighborhood of 5,000 to 6,000 bbls. per day of liquid hydrocarbons, there are produced approximately 6900 lbs. per day of butyraldehyde and 2300 lbs. per day of ethyl acetate. Specifically, the mixtures of butyraldehyde and ethyl acetate thus obtained usually contain from about 50 to '75 weight per cent butyraldehyde, 20 to 40 weight per cent ethyl acetate, and from about 3 to about '7 weight per cent water. Distillation of such a mixture is ineffective to separate these two chemicals owing to the fact that their in dividual aqueous azeotropes as well as the individual pure compounds boil only 2.4" C. apart, as noted above.

Accordingly, it is an object of my invention to provide a method whereby butyraldehyde can be obtained in substantially anhydrous form and substantially free from objectionable amounts of ethyl acetate by distillation of mixtures ofthese compounds in the presence of water at subatmospheric pressures, for example, from about 50 to about 250 mm. It is a further object of my invention to remove solubilized water from the wet butyraldehyde and ethyl acetate thus separated by first allowing these mixtures to collect in individual settling tanks and thereafter subjecting the resulting product layers to distillation to obtain in one case an overhead of butyraldehyde-water azeotrope and a dry butyraldehyde residue and in the other case an overhead of ethyl acetate-water azeotrope and a dry ethyl acetate bottoms portion.

The above and other objects of my invention areefiect'ed by employing a system of the type shown in the accompanying drawing wherein acha'rging stock, for example, comprising essentiallyan aqueous solution of butyraldehyde, ethyl acetate; methyl ethyl 'ketone, methyl propyl ketone, isopropyl alcohol, and ethanol, obtained by the hydrogenation of carbon monoxide in the presence of afluidized'iron catalyst, is introduced into column 2 through line 4. In this column the feed is subjected to an extractive distillation operation by the introduction of water at a pointnear the top of the column through line 6 where the'hot rising vapors of the feed mixture are contacted by the descending water stream. Generally,to effect a satisfactory sepa'ration of butyraldehyde and. ethyl acetate from methyl 'ethylketone, methyl propyl ketone, isopropyl alcohol, and ethanol at this point, the dilution water added through line '5 should be introduced in an amount such that the concentration of water in the liquid at any point in the column is from about to 99 mole per cent and preferably about mole per cent. The amount of net overhead withdrawn should be carefully controlled to avoid forcing methyl ethyl ketone, methyl-propyl ketone, ethanol, or isopropyl alcohol overhead or butryaldehyde and ethyl acetate into the bottoms at this stage. Ordinarily, the heat input should be in the range of 80 to B. t. u; per lb. of bottoms, preferably about 90 B. t. u. per lb. of bottoms. It has been my observation, however, that the use of an excessive amount of heat impairs the efliciency of the column since, under such conditions, the concentration of water in the column falls below the value suitable for effecting the desired separation. The temperature employed in carrying out this operation may vary; however, I may generally employ bottom tower temperatures of from about 82 to about 94 C. (cor rected to atmospheric pressure), preferably about 85 C., and top tower temperatures of from about 68 to about 77 0., preferably 71 C. The-bottoms stream which consists of an aqueous solution ofmethyl ethyl ketone, methyl propyl ke 3 overhead stream is sent through line 8 into cooler I i where it is chilled after which it is passed into separator it and allowed to stratify into two layers, the upper one of which consists of butyraldehyde and ethyl acetate together with some solubilised water. The lower. water layer contains a small amount of'solubilized ethyl acetate butyraldehyde and is returned to column 2 through line It. which, under these circumstances,, consists. of about 72 weight per cent butyra-l'dehyde, 24 weight per cent ethyl acetate, and 4 weight per cent water, is then sent through line 2% where it is mixed with additional water from lines is 53 and thereafter introduced into column from separator It through line so is already saturated with respect to water, it will be apparent that the addition of'water thereto through lines and 55 will produce a heterogeneous aqueous mixture of butyraldehyde and ethyl acetate prior U the distillation step carried out" in: column 22. The formation of a heterogeneous mixture at this pointis desired in the operation of my process and the amount of. water introduced into line fidnvi'a' lines t0 and should be at least enough so that-the individual aqueous azeotropes of butyraldehyde and ethyl acetate can be formed but should not-be more than about 50 per cent based on the weight of chemicalsv charged to column 22. Expressed otherwise, the Water content of the feed stock: charged to column 22 should generally be in they range of from about 9 to about 35 weight per cent.

The feed introduced into column 22 is then subjected to fractional distillation under reduced pressure to withdraw awet overheadof' butyraldehyde through line 2 4 and condenser-2'0, a portion there-of being returned to the column through line 28 as reflux. In this connection, thereflux ratio maintained in column- 22" should generally be in the range of" from about 5:1 to about :1. The balance of: the overhead stream is conducted through line 24 to separator 3 B where the resulting distillate separates: into two layers;

the lower water layer is ing returned'through line 32 to column 22. The bottoms obtained in this distillation operation consists essentiallyof ethyl acetate together with water inat least azectropic amounts and is withdrawn through line 34 and cooler 35 after which" it" is introduced into separator lit. The water layer thus formed is. returned to column 22 via lines 4% and 20., Periodically, water may be purged from the" system through valved line 42.. In column 22 the conditions necessary to effect the desired separation of butyraldehyde from ethyl acetate may vary rather widely. Thus, in'the top of the column, the pressure may range from about 5'0 to about 250 mm... preferably aboutlfitl'mml, and thetemperature may range from-about 2 to aboutg35or 40 C. preferably about 25 (7: Bottom pressures and temperatures should generally be maintained in a range of from about 200 to about 4.00 mm,, preferably about 250.mm., and from about 38 to about 65 C., preferably about 52C., respectively.

The organic layer in. separator 39 which consists essentially of. butyraldehyde, together with about 3.5 weight per cent of. water,.is withdrawn through line M and introduced into. column Mi which is operated at atmosphericpressure or above to increase the eiiiciency of the butyraldehyde drying operation. At atmospheric pressure the butyraldehyde-water azeotrope contains 12: weight per cent water-and within limitsthe quan- The organic layer Since the organiclayer withdrawn:

tity of azeotropic water may be increased by increasing the pressure. Excessive pressures are to be avoided since the temperatures necessary to vaporize the feed at such pressures causes polymerization of the butyraldehyde. In the maioritypf: instances; however, I prefer to employ pressures up: to about 40. p; s. i. a. In this distillation, an overhead of butyraldehyde-water azeotrope is withdrawn through line at and condenser 511, allortionthereof being returned to the column. as, reflux through line 52'. The major portion of the overhead stream passes into separator-Bil wherethei organic layer of Wet butyraldehyde (contains about 3.5 Weight per cent water)" is' returned through line 56 to column 5 for. elimination of, water. The Water layer in separator 54 is returned to column 22 via lines 58 and 2.0 and a dry butyralde-hyde bottoms of approximately $3 1 to $9 weight per cent purity is withdrawn from column 46 through line tit. Alternatively, butyraldehyde may be removed from. column; 46- in vapor form, through a side draw-off line M and, converted to liquid in condenser-49. The butyraldehyde obtained in this mannerianormally entirely free from polymeric products. Inthe event butyraldehyde is recovered from column Mlin thismanner, line 60 may be used as a purge line to prevent the concentration of undesirable impurities from building up in the system. The organic layer in separator stwhichconsists of wet ethyl acetate (contains about 3.8 Weight per cent water) is Withdrawn through line 62 and introduced into column 6 1 operated at atmospheric pressure or above, for example, up to about 50 p. s. i. a. The overhead iraction-obtainedin this operation consists of the ethyl; acetate-Water azeotrope and is withdrawn through line $6 andoondenser 68, part of which is returned to the column through line 72! as reflux. The; organic layer in separator 12, consisting; of ethyl acetate together with about 3.3 weight per cent water, is returned to the column throughline 'iirtwherethe remaining water is reiected. The lower water layer in separator i2 is withdrawn through line'l i and combined with thflwatel inline; iii. A, dry: ethyl acetate bottomsof about 9-7, weight per cent purity is withdrawn from column 84 through line it. In this drying operation the pressure within'the distillation column is preferably at least equal to atmospheric pressure; From theoretical considerationa. it isindicated that increased drying ef ficiency' is achieved with increased pressures; howevenior practical reasons I have found that adequate drying can be accomplished at pressures not substantially in excess of 50 p. s. i. a.

One of the outstanding and surprising features of. my inventionresides in the separation of butyraldehyda from ethyl acetate by vacuum distillation: of mixtures thereof in the presence of water, notwithstanding the fact that I have been unable to, accomplish this object either by dry vacuum distillation. or by means of wet distilla tion' of such mixtures at atmospheric or higher pressures. Thisfact is even more surprising inasmuch as the vaporpressure curves for butyraldehyde and ethyl acetate indicate a sufficient spread in the respective boiling points of these compounds at the, pressures contemplated, to render possible the separation of these chemicals, in anhydrous form, by means of ordinary vacuum distillation.

The process of my invention may be further illustrated by, the. following specific, example wherein the improved efficiency thereof over dry vacuum distillation and wetdistillatiori at v atmospheric pressure is plainly demonstrated.

Three samples, two of which contained 414 m1.-

the scope thereof. In general, it may be said that the use of any equivalents or modifications of procedure which would normally occur to one skilled in the art is to be-included within the scope of my invention. of ufiyl d yd 85 ml. of ethyl acetate, and The expressions wet butyraldehyde and "wet 200 ml. of water, While the third sample consisted ethyl acetate herein referred to are to be interof 414 ml. of'butyraldehyde and 185 ml, of ethyl preted as homogeneous quantities of butyraldeat wer c sively introducedinto a highly hyde or ethyl acetate containing solubilized water. eflicient fractionating' column under the condi- Also, unless otherwise specified, the pressure tions indicated below. At regular intervals, in ranges given herein are intended to refer to the each case,,fractions of distillate werecollected permissible pressures prevailing at or slightly and analyzed. below the point in the distillation column of over- I. head vapor "withdrawal.

Wet distillation at 120 mm.

OVerIlLeIadVoLe Analysis of Organic Layer iz ig Overhead can Gut NO i Wt. per Wt. per-' wil Total .5 g g g, 353?" r 'ayer we: Acet te We 1 Collected in Dry Ice trap ahead of vacuum pump.

e TABLE II V Wet distillation at'atmospheric pressure gffi Analysis of Organic Layer wt cent B11- Out l g g i wt. per- Wt. perw 51 331? we t s it: as. its aye? h yde Acet te water a 1 68.1-67.8 110.6 50.0 88.0 8.0 4.0 01.7 2 67. 8-67. 8 123.5 50.0 84. 7- 11.2 41 88.3 3 67.8-72.2 140.5 60.8 80. 0, 14.2 85.1 4 72.2-67.8 124.4 50.0 81.8 14.1 4.1 85.8 5. 67. 8-878 113.3 51.0 82.4 13.8 3.8 85.7

1 200 ml. of water added to the still before cutNo. ewes made.

TABLEIH a c aim 1s: my vacuum dlstlua'twn 1. In a process for separating butyraldehyde wt Percent from an aqueous mixture of ethyl acetate, the can g g g t i steps which comprise subJectmg a heterogeneous hyde mixture of butyraldehyde and ethyl acetate containing water in a concentration of from about 9 g g to about 35 weight per cent to fractional distilla- 1 121 1 55 tion at pressures of from about 50 to about 250 fag-3 a mm. and collecting an overhead of butyralde- 5010 121 87:8 hyde-water azeotrope and a bottoms fraction of I ethyl acetate and water.

The true value of each of the procedures set In a process o bta ning butyraldehyde in forth in the above example can be ascertained a substantially pure state from aqueous mixtures when it is recognized that the best results obof oxygenated Organic Compounds 0f the ype tained in each of the three individual processes produced in the he s of hydrocarbons from represent the efficiency that is possible when carbon monOXide and y en, aid mixtures operating on a continuous basis t d of containing ethyl acetate and methyl ethyl ketone, batchwise operation. Thus, when operating 'con- 5 the steps W c comprise subjecting said mixture tinuously in accordance t th present i to fractional distillation in a column in which a. tion, butyraldehyde f per t purity can be heat input of from 80 to 120 B. t. u. per lb. of hotobtained; however, when operating under the toms is employed to g ve a bottom tower temperrespective conditions pecified by Tamas II nd ature of from about 82 to about 94 C. (corrected III, butyraldehyde of only 91.7 per cent and 89.5 to phe ic pressure) and an overhead temper cent purity can be produced. perature of from about 68 to about 77 0., intro- It will be apparent in view of the foregoing ducing water into said column in an amount such description and data appearing above that the that the concentration of water in the liquid at process of my invention may be modified in nuany point in the column is from about 90 to about merous ways without materially departing from 99 mole per cent, withdrawing an overhead s ream. Qf: but raldeh-yda wa -i. nd: hyl.- we: atesubieqtine;sa d:. v rheed r mo r t na it .i la u;v at ur ssur s from abou 2. 0- utbs message- Q rom; bqu 9 to about 3. weight per cent water, collecting a distillate. of but alqe rdefl ater a e t o a, o n t ut ra de rda he eimmi t e afte subjecting. he et u ldehrde sq r r to f a n I I neinen'om bo t a J heric; pressure to about, 40 p. s. i. a., and w thdr win r ead a utyml e de-wate aaeotrope, leaving a bottoms, fraction of; dry sub.-v stantiellr time: utrral ehyde- 3. In a process for obtaining butyraldehyde in a substantially pure state from aqueous mixtures of oxygenated organic compounds of the type produced in the synthesis of hydrocarbons from carbon monoxide and hydrogen, said mixtures containing ethyl acetate and methyl ethyl ketone,

the steps which comprise subjecting said mixture to fractional distillation in a column in which; a heat input of from 80 to 120 B. t. u. per lb. of; bottoms is employed to give a bottom tower temperature of from about 82 to about 94 C. (corrected to atmospheric pressure) and an overheadtemperature of from about 68 to about 77 0., intro ducing water into said column in an amount such that the concentration of Water in the liquid at any point in the column is from about 90 to about 99 mole per cent, withdrawing an overhead stream of butyraldehyde, water, and ethyl acetate, subj ecting said overhead stream to fractional distillation at pressures of from about 50 to 2501 mm. in the presence of from about 9 to about 35 weight per cent water, and collecting an overhead of butyraldehyde-water azeotrope and a bottoms fraction of ethyl acetate and water.

4. In a process for separating butyraldehyde from an aqueous mixture of ethyl acetate, the steps which comprise fractionally distilling a heterogeneous mixture of butyraldehyde and ethyl acetate containing not more than 50 weight per cent water but at least sufficient water to form the individual aqueous azeotropes of butyraldehyde and ethyl acetate at a pressure of between about 50 and about 250 mm. Hg and separating an overhead of butyraldehyde-water azeotrope from a residual fraction of ethyl acetate and water.

a grosses; or epar ting bu rr yfi from apartment he la t r t i hfl te. the steps which comprise adjusting the water content of said mixture to a concentration of from: a out 9.. o abo 3 per nt, thereaf, r subjecting the resulting mixture to fractional; distillation at pressures oi from about to. about 250 mm. and collecting an overhead oi? butynaldehyde-water azeotrope and a bottoms fraction. of; ethyl acetateand water.

6.111, a processfor separating butyraldehyde troma, mixture containing the latter and ethyl acetate, the steps which comprise adjusting the water content of said mixture to a concentration corresponding to not more than 50 wt. per cent of; said3mixture but at least sufficient water to form thev individual aqueous azeotropes of butyraldehyde andethyl, acetate, thereafter subjecting the resulting mixture to fractional distillation at, a pressureofbetween about 50 and about 250 mm. and separating an overhead of butyraldehyde water azeotropev from a residual fraction of ethyl acetate and Water.

THEODORE Q. ELIOT.

References Cited in the file of thi patent UNITED STATES, PATENTS Number Name Date 1,556,057 Bogin Oct. 6, 1925 1,676,700 Lewis- July 10, 1928 1,724,761 Holden Aug. 13, 1929 2,290,636 Deanesly July 21, 1942 2,321,748 Hopkins et al June 15, 1943 2,324,255; Britton et a1 July 13, 1943 ,398 68 Bloomer -.-.-.-V--V-.-- Ap 1 1 2,54 & i 7, Harney, Jr., et a1. Nov. 23, 19 18 2,476,391 1 Stantzenberger et a1. July 19, 1949 OTHER REFERENCES Young, DistillationPrinciples and Processes, cop ri ht 1922 by MacMillan and (30., Limited, London, pages 59-61. (Copy in Div. 25.)

Analyticalz Chemistry, vol. 19, page 51 0, August 1.9 v Tab e. o A otrpp s nd N n z compiled. by L, Horsley. (Copy in Patent Ofiice Library.) 

1. IN A PROCESS FOR SEPARATING BUTYRALDEHYDE FROM AN AQUEOUS MIXTURE OF ETHYL ACETATE, THE STEPS WHICH COMPRISE SUBJECTING A HETEROGENEOUS MIXTURE OF BUTYRALDEHYDE AND ETHYL ACETATE CONTAINING WATER IN A CONCENTRATION OF FROM ABOUT 9 TO ABOUT 35 WEIGHT PER CENT TO FRACTIONAL DISTILLATION AT PRESSURES OF FROM ABOUT 50 TO ABOUT 250 MM. AND COLLECTING AN OVERHEAD OF BUTYRALDEHYDE-WATER AZEOTROPE AND A BOTTOM FRACTION OF ETHYL ACETATE AND WATER. 